Such a piston/cylinder unit is known from U.S. Pat. No. 5,525,845 A. In this known piston/cylinder unit outlet nozzles are provided in the cylinder wall which support the piston in its first piston position and in its second piston position. In order to make this possible, the outlet nozzles are located relatively far from the cylinder base, that is from the front inner wall of the cylinder bore. This has the consequence that the fluid cushion formed between the piston circumference and the inner circumference of the cylinder for bearing the piston in the cylinder in the area of the front circumferential region adjacent to the piston base becomes weaker, the further the piston migrates into its second piston position, that is the compression position. As a result of the high pressure produced simultaneously during the compression in the cylinder volume, compressed fluid penetrates from the cylinder volume into the bearing gap between the outer circumference of the piston and the inner circumference of the cylinder which, when this penetrates asymmetrically along the circumference, results in a lateral deflection of the piston and therefore in undesired tipping of the piston.
Known from JP 2002-349 435 A is a piston/cylinder unit which is driven by a linear motor and is guided freely on a gas cushion in the piston-ring-free piston. For stabilising this gas cushion, the piston is provided with a circumferential groove on its circumference. This circumferential groove is designed to reduce the risk of the piston tilting in the cylinder. The circumferential groove not only weakens the transverse force disadvantageously for the bearing of the piston but also the air bearing as a whole so that the effect of the circumferential groove relative to the air bearing is rather disadvantageous.